Background: Iraq and Afghanistan war (OIF/OEF) Veterans have experienced repeated deployment- related stressors that put them at risk for health conditions that can negatively impact their post-deployment readjustment. Employment is a key indicator of successful reintegration, but OIF/OEF Veterans are less likely to be employed than their civilian counterparts, identifying difficulties at work and job loss as barriers to readjusting to civilian life. Additional challenges include psychiatric conditions, including posttraumatic stress disorder (PTSD), which is estimated to affect approximately 20% of OIF/OEF Veterans. Among the 5% costliest patients receiving VA care in fiscal year 2010, 17% had a PTSD diagnosis. Among these, their inpatient cumulative behavioral length of stay was 3.6 days, and outpatient utilization included 18.6 mental health visits, 1.8 emergency department visits, 6.5 primary care visits, and 5.2 subspecialty visits. Unemployment and service-connected disability in OIF/OEF Veterans has the potential to increase VA acute care service utilization, which may strain and have a long-term impact on VA resources, given that the OIF/OEF cohort will likely use VA services for six more decades. Interventions that assist Veterans in recovery and return to employment are expanding in the VA, but little is known about how these evidence- based interventions and subsequent return to work impacts the health service utilization patterns in unemployed Veterans with PTSD. This study seeks to gather this evidence to inform policy and practices in the delivery of the most effective vocational rehabilitation program for Veterans with PTSD. Methods: This study will evaluate the health service utilization among recently unemployed Veterans with a diagnosis of PTSD who have been randomized to receive either Individual Placement and Support (IPS) or Transitional Work (TW). IPS is an evidence-based model of supported employment, which is an assertive, person-centered, patient-driven approach to vocational rehabilitation. VA IPS has been available to Veterans with severe mental illness and to those who are homeless, but has not been accessible to Veterans with a primary diagnosis of PTSD. In 2013, under the leadership of Dr. Davis, VA Cooperative Studies Program (CSP) launched a multisite randomized controlled trial comparing the effectiveness of IPS to TWP for Veterans with PTSD (n=541) in terms of employment outcomes, PTSD symptoms, self-esteem and quality of life. This large, prospectively randomized, geographically diverse group of unemployed Veterans with PTSD represents a unique opportunity to learn more about the impacts of IPS on health care utilization. The specific aims of this study are to 1) compare the acute care utilization in Veterans with PTSD prospectively randomized to IPS versus TW; 2) compare the costs for high intensity services (i.e. inpatient, ED, domiciliary, residential) services and for outpatient services among Veterans with PTSD randomized to IPS versus TW; and 3) assess the cost-effectiveness of IPS relative to TW among Veterans with PTSD. Significance: Despite a decade of IPS implementation and a world-class medical record system within VA, no research has been conducted to evaluate the impact of IPS compared to TWP within VA on health care service utilization in a PTSD population. However, the strong evidence for reduction in acute care services among persons with serious mental illness randomized to IPS from US and international randomized clinical trials compels us to learn more about IPS in the VA setting and in a PTSD population. As more evidence emerges about the clinical effectiveness of IPS, stakeholders eagerly want to know if IPS has the potential to reduce the use of high intensity acute care services and potential cost effectiveness. This first-of-its-kind study is landmark given its timeliness, size (n=541), prospective randomized controlled design, VA setting, diagnostic focus (PTSD), use of computerized patient records from a fairly closed health care system (VA), comparative interventions (IPS/TW), and distinguished team of investigators.